INTRODUCTION.
Some would say that damaged old slides are
better left alone, but sooner or later one reaches that stage
when the risk of incurring serious or terminal damage becomes
an acceptable option. The illustrations cover the renovation
of an example donated by a collector from Northern Wales.
(Slide of 'Gizzard of
Cricket' with broken coverslip)
Coverslip
breakage is probably the most common damage to old slides,
much of it dating to the good old days before parfocal
objectives were introduced.
It may well be that the coverslip is actually more or less
whole but it has become obscured by particles from the
objects like spores that have become attached to the
underside of the slip. Slides stored in damp inappropriate
situations like lofts or garages may be engulfed in fungal
growth. A common enemy of the would be conservator.
Alternatively the objects may have become detached from the
black background or they may have become severely tarnished
by dust and require cleaning and remounting.
REMOVAL
OF THE UPPER PAPER.
Usually there is a single rectangular paper
on the upper surface of the slide which is entire except for
a 16-19mm aperture for viewing.
(The wet tissue laid on
slide for 15 minutes only)
A
4"X1" strip of kitchen towel tissue is cut from a
roll.
This is laid over the slide and enough plain water is dripped
onto it with a pipette so that it becomes thoroughly
saturated but not overflowing with water. After 20 minutes
the strip can be removed and the upper paper can be carefully
removed. It will become at once apparent that the remains of
the coverslip are more of less still stuck to the paper and
that all the gum that was used had been water soluble. If the
paper is reversed in a sink, a model paint brush and water
can be used to brush off the slithers of glass and if it is
turned over the brush can also be used to free the dirt that
has built up on the surface.
Awkward stains
may be removed by very dilute soapy water, but avoid solvents
or the ink may disappear. Most of the ink used by Victorians
was water fast or became water fast after a period of time.
The whole cleaning process should only take a few minutes.
Prolonged treatment would also loosen the lower paper. After
rinsing, the paper rectangle may be carefully dried in a flat
inverted position. It will be hopefully free of gum, glass
and much of the dirt.
(The upper paper removed)
REPLACING THE
COVERSLIP.
If the objects are clean and secure on the
black patch, then a new coverslip may be applied. The most
satisfactory method is to invert the paper inside a large box
lid and spray with 3M Photo adhesive. When dry the coverslip
of the correct dimensions can be laid in the creases left by
the broken one and carefully the paper with slip attached can
be replaced on the slide. This 3M product which is a contact
adhesive, allows a small amount of adjustment if the
placement is not precise enough. Dry mounts which are not
subjected to very high power objectives are better provided
with a thicker cover glass and anything less than Number 2 is
to be avoided. A diamond pencil may be used to cut glass from
a larger slip if necessary
IMPROVING
THE OBJECTS.
If dry objects like foraminifera are loose,
freshly made gum tragacanth may be used to secure them. To be
authentic most of these displays used to conform to some sort
of geometric pattern and it is as well to try to try and
reproduce this. Broken objects can be replaced if one has a
supply of any of these. A Number 1 art brush and a Number OOO
art brush may be used for manipulation, remembering that a
Number 1 may also be used to withdraw excess of fluid if it
is first wiped on a paper towel.
The work must be gently dried before sealing avoiding excess
heat as such. Objects like the gizzard that are embedded in
something like gold size or even black paint rarely require
treatment.
(Completed work with coverslip replaced)
CELLS
FOR LIEBERKÜHN ILLUMINATION.
The very small black mounting area
surrounded by an annulus of clear glass is an indication that
the cells were designed to be viewed under Lieberkühn
illumination and its a good idea to take this opportunity to
clean it thoroughly with a tiny pad of tissue dampened in
distilled water and held by forceps.
Calcareous remains that have become grey will respond to
removal by a damp brush and several days in hydrogen
peroxide. The objects can be replaced after the patch has
been cleaned or repainted with NBS mat black paint Again the
gum tragacanth that leaves little in the way of a smear is
one of the best adhesives.
FURTHER
CONSIDERATIONS.
Old slides are becoming increasingly
valuable items and renovation is a risky business. Experience
should first be gained on examples that are beyond hope
before more worthy slides are tackled with appropriate
caution.
MATERIALS
REQUIRED.
Gum tragacanth, 3M photo mount, distilled
water, NBS black background paint, hydrogen peroxide, paper
kitchen towel, art brushes No. 1 and 000.
Comments to the author Brian Darnton welcomed.
Visit Brian Darnton's home pages.
Related Micscape articles by the author.
The construction of a Victorian type dry mounted slide.
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Published in the March 2000 edition of Micscape Magazine.
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